The present invention relates to a clamping device, such as a screw or nut, for clamping a rotating tool or stationary object, such as a grinding wheel, circular saw blade, etc., to a threaded drive spindle.
When attaching a rotating tool to a drive shaft of a power tool, in conventional practice a flange and a male thread are formed at the end of the drive shaft and the rotating tool is inserted over this male thread. A clamping nut having a female thread is screwed onto the threaded drive shaft and clamps the tool against the flange. Typically, a tightening tool such as a wrench is needed to tighten the clamping nut onto the drive shaft and also to loosen the clamping nut to change out the tool.
One downfall of the use of an external tool, such as a wrench, for tightening the clamping nut as described above, is that alignment of the power tool may become unbalanced and its work performance may deteriorate. Additionally, in many applications, it is cumbersome, if not impossible, to fit a wrench or other tightening device onto the clamping nut depending on the working application of the power tool. Thus, if the clamping nut can be attached by manual rotation only, work performance and efficiency can be greatly improved.
However, when the nut is rotated in a manual operation, a loss in clamping force occurs due to frictional resistance in the threaded portions of the shaft and clamping nut, with the difficulty that it is not possible to create a sufficient clamping force in the manual operation alone. Additionally, there is also the possibility that a tightening thrust of the rotating tool imparted to the clamping nut will cause the clamping screw to overtighten if left unchecked to the point where it is impossible to remove the clamping nut in a manual operation.
The present invention relates to an improved clamping device that enhances or increases a manual clamping force while also checking or limiting overtightening of the device from operational thrust of the rotating tool so that the clamping device is readily removed in a manual operation.